The present invention relates to a developing device and an image forming apparatus for forming an image.
In an electro-photography type image forming apparatus as a conventional image forming apparatus, a charging roller as a charging member is arranged to uniformly charge a surface of a photosensitive member as an image supporting member. An exposure unit is arranged to form a static latent image on the photosensitive drum, and a developing device is arranged to form a toner image on the static latent image on the photosensitive drum. The developing device includes a developing roller as a developer supporting member; a supplying roller as a developer supplying member for supplying toner as developer to the developing roller; and a regulating blade as a developer layer forming member for forming a toner thin layer on the developing roller.
In the conventional image forming apparatus, after the toner image is transferred to a sheet, a cleaning blade formed of a rubber plate member is arranged to collect toner remaining on the photosensitive drum. Further, a fixing device is arranged to fix the toner image on the sheet, and the sheet is discharged outside the conventional image forming apparatus. The conventional image forming apparatus may include a plurality of developing devices arranged in series for forming toner images in four colors, namely, black, cyan, magenta, and yellow, so that it is possible to form a color image.
In the conventional image forming apparatus described above, it may configured such that a toner supply voltage applied to the supplying roller is controlled according to a detection result of toner attached to a non-exposed region of the photosensitive drum or an area of a transfer member corresponding to the non-exposed region of the photosensitive drum. Accordingly, it is possible to prevent a stain from generating on the sheet (refer to Patent Reference).    Patent Reference: Japanese Patent Publication No. 2007-093775
In the conventional image forming apparatus disclosed in Patent Reference, it is configured such that the toner supply voltage applied to the supplying roller is controlled, so that an amount of toner supplied to the supplying roller is adjusted. However, when an outer circumferential portion (a rubber portion) of the supplying roller is worn out, the amount of toner supplied to the supplying roller tends to be excessive, thereby causing a stain on the sheet.
In view of the problems described above, an object of the present invention is to provide a developing device and an image forming apparatus capable of solving the problems of the conventional developing device and the conventional image forming apparatus. In the present invention, it is possible to reduce a stain generated on a sheet.
Further objects and advantages of the invention will be apparent from the following description of the invention.